Manitowoc 16000 User Manual

Reference Only
HOISTS 16000 SERVICE/MAINTENANCE MANUAL
5-4
Published 05-03-17, Control # 228-03
BLOCK-UP LIMIT
A block-up limit (also called an anti two-block device) is a
two-blocking prevention device that automatically stops the
load drum from hoisting and the boom from lowering when a
load is hoisted a predetermined distance.
Two-blocking is an unsafe condition when the load block or
weight ball contacts the sheave assembly it is suspended
from.
Two-blocking can cause sheaves and wire rope to fail,
possibly causing the load to fall.
The block-up limit system consists of the following
components (see Figure 5-4
):
• A normally closed limit switch assembly fastened at the
following locations:
- Lower boom point
- Upper boom point
• A weight, freely suspended by chain from each limit
switch actuating lever, that encircles the load line as
shown.
• A lift block fastened to the load line, or lift plates fastened
to the load block.
Operation
See Figure 5-4 and Figure 5-5 for component identification.
For a complete wiring diagram of the system, see the Boom
Wiring and Limits Drawing in Section 3.
Block-Up Limit Control Deactivated
During normal operation, the weight overcomes spring force
and rotates the actuating lever away from the limit switch
lever. This action allows the limit switch to close the load
drum up and boom down electric circuits. Therefore, the load
can be hoisted and the boom can be lowered.
Block-Up Limit Control Activated
When the weight is lifted by the lift block or lift plates, spring
force rotates the actuating lever against the limit switch lever.
This action causes the corresponding limit switch to open the
load drum up and boom down electric circuits.
The load drum and boom/mast hoist pumps stroke to off. At
the same time, the load drum and boom parking brakes
apply to stop the load drum from hoisting and the boom from
lowering.
WARNING
Two-Blocking Hazard!
The block-up limit is a protective device designed only to
assist the operator in preventing a two-blocking condition.
Any other use is neither intended nor approved.
The block-up limit may not prevent two-blocking when the
load is hoisted at maximum single line speed. The
operator shall determine the fastest line speed that allows
the block-up limit to function properly and, thereafter, not
exceed that line speed.

Manitowoc 16000 Specifications

General

Brand	Manitowoc
Model	16000
Category	Construction Equipment
Language	English